Ceramic powder having a perovskite crystal structure, e.g., powder of barium titanate (BaTiO3), is widely employed as a dielectric material for use in manufacturing ceramic electronic components such as multi-layer ceramic capacitors. Nowadays, there is an ever-increasing demand for miniaturization of ceramic electronic components. For the miniaturization of a multi-layer ceramic capacitor, for example, thinning of dielectric layers incorporated therein, i.e., thinning of green sheets, needs to be accomplished, which requires a finer ceramic powder with an improved crystallinity of crystal lattice thereof.
The perovskite-structured ceramic powder is manufactured by a synthesis method such as a hydrothermal method, a hydrolysis method, a solid phase synthesis method, an oxalate method, a citric acid method, a gas phase synthesis method, and so forth. Though using any one of these methods allows ceramic powder having a particle diameter of 0.2 μm or less to be obtained, the hydrothermal method or the hydrolysis method is the most preferred among them in general, for such wet methods are more adequate for producing finer powder (see Japanese Patent Laid-open Publication Nos. 2002-234771 and 2001-316114).
In the wet methods, however, OH groups enter a crystal lattice during a synthesizing process, which results in a low crystallinity and a degraded dielectric characteristics. To solve such problem, synthesized ceramic powder is conventionally reheated in the atmosphere for the purpose of removing the residual OH groups in the crystal lattice. Though such reheating has positive effects of inducing a grain growth and improving the crystallinity of crystal lattice and the dielectric characteristics, it also causes an increase in a volume ratio of portions that does not contribute to a dielectric constant since regions within the particles where the OH groups were once present are left in a form of vacancies, thereby lowering a dielectric constant.